In the electronics industry, connection pins are widely used to provide connection between different parts of an electronic assembly. The connection pins are e.g. mounted in a through-hole in a component carrier or they are surface mounted to a component carrier, which component carrier can have different applications and/or combinations thereof, such as: the component carrier can be part of a printed circuit board, it can carry electronic components and form a component board, it can carry modules such as power modules or stackable modules comprising different components, it can be part of a motherboard etc., all of which can form, or be parts or modules of an electronic assembly. The connection pins usually provide both mechanical connection between the parts of the assembly, as well as electrical connection. There exists a number of known assembly techniques for anchoring a connection pin in or to a component carrier, such as wave soldering, surface mounted pin in solder paste, press-fit, rivet/clinching, etc. The chosen technique mostly depends on the application in which the component carrier is used and the requirements involved.
When using a press-fit assembly technique, the component carrier is provided with a through-hole into which an end portion of the connection pin is to be inserted. The through-hole is slightly narrower than the end portion of the connection pin, and the connection pin has to be inserted into the through-hole by force, thereby achieving a press-fit of the connection pin in the through-hole. The interior wall of the through-hole and/or the press-fit portion of the connection pin are subject to deformation. The connection pin may have a press-fit portion that has a special design in order to facilitate deformation. Examples of such connection pins adapted for press-fit are found in WO 2007/008264 and US 2009/0298312.
According to another known assembly technique, the connection pin has an end portion adapted to be inserted in a through-hole in a component carrier, which end portion is slightly narrower than the size of the through-hole. The connection between the connection pin in the through-hole and the component carrier is achieved by dispensing solder paste in the through-hole, or at the opening of the through-hole, and soldering the connection pin to the component carrier.
According to another known assembly technique, the connection pin may be designed as a rivet and will then be anchored to the component carrier by riveting to the connection pin. In order to provide electrical connection between the component carrier and the connection pin, the connection pin is usually also soldered to the component carrier.
In many applications, each connection pin is anchored to a component carrier via one of its ends, and the other end of the connection pin is intended to be mounted on the surface of another module in the electronic assembly, such as another component carrier, a printed circuit board (PCB), a motherboard, a component board, etc. Whenever such surface mounting is used, one important factor is the tolerances between the different parts. For example, the tolerance related to the distance between the end of each pin facing the surface on which it is to be mounted and the surface itself, is crucial if successful mounting is to be achieved. Since the mating surface of the module on which the component carrier with its pins are to be mounted generally has a high degree of planarity or flatness, the corresponding end surfaces of the connection pins must also represent a common surface with a high degree of planarity/flatness, or in other words, a high degree of co-planarity between the end surfaces. However, this can be a problem, often due to the fact that the anchoring of the pins in the through-holes of the component carrier nearly always involves some sort of deformation of the pin in its longitudinal direction, and/or the through-hole and/or the component carrier. If the component carrier is deformed e.g. when riveting a connection pin, this will result in a slightly curved component carrier with deficient planarity and the connection pins anchored in the component carrier will also display a corresponding deficiency of co-planarity of their end surfaces facing the mating surface. If the connection pins are deformed in their longitudinal direction this will affect the flatness/planarity of their end surfaces, both in terms of the individual end surface perhaps not being totally aligned with the intended mating surface, and in terms of the previously referred too common surface represented by the end surfaces of several connection pins, not having the required high degree of co-planarity. Also the assembly technique of soldering the pin in a through-hole can result in lack of sufficient planarity. A typical failure in electronic assemblies as described above occurs when the lack of co-planarity of the connection pins of a mounted device, such as a component carrier, impedes the soldering of an intended mating surface which will result in an air gap and lack of electrical connection between the pin with its device and the mating surface.